TW201425221A - Method for producing polycrystalline silicon - Google Patents

Abstract

A method for producing polycrystalline silicon, which comprises: a silicon deposition step wherein silicon is produced by a reaction between a chlorosilane compound and hydrogen; a conversion reaction step wherein the exhaust gas discharged during the silicon deposition step is brought into contact with activated carbon, so that hydrogen chloride in the exhaust gas is removed; a separation step wherein hydrogen in a post-conversion-reaction gas obtained in the conversion reaction step is separated; and a circulation step wherein the hydrogen obtained in the separation step is supplied to the silicon deposition step. This method for producing polycrystalline silicon is characterized by satisfying the condition (1) and/or condition (2) described below. (1) The post-conversion-reaction gas obtained in the conversion reaction step is brought into contact with an adsorbent that contains a Lewis acidic compound before the separation step. (2) The hydrogen obtained in the separation step is brought into contact with an adsorbent that contains a Lewis acidic compound before being supplied to the silicon deposition step.

Description

Polycrystalline germanium manufacturing method

The present invention relates to a method of producing polycrystalline germanium. More specifically, the present invention relates to a method for producing a polycrystalline silicon, comprising: removing hydrogen chloride from an exhaust gas discharged from a deuterium precipitation step, and recycling the recovered hydrogen to the step of the above-described decanting step, which can be easily and effectively The phosphorus-containing impurity from the activated carbon of the hydrogen chloride-removing catalyst is removed.

As a method for producing polycrystalline silicon used as a raw material for a semiconductor or a solar power generation wafer, a gas-liquid deposition method, a Siemens method, or the like has been known. These methods are techniques for decanting the surface of the substrate by contacting a chlorodecane compound (especially trichloromethane) and hydrogen with a surface of a substrate having a high temperature set in the reactor. With these techniques, there is an advantage that polycrystalline germanium of very high purity can be obtained. On the contrary, in the exhaust gas discharged from the reactor, dichlorosilane, hydrogen, hydrogen chloride or the like is contained, and in particular, disposal of hydrogen chloride is a problem. When hydrogen chloride is discarded, hydrogen chloride is separated from the exhaust gas by the adsorption method, so it is necessary to neutralize it with a base. The cost of equipment and operation for this separation process and neutralization process is very high. Therefore, in order to industrially produce high-purity polycrystalline silicon by the above-mentioned technology, the exhaust gas is exhausted. The processing cost of hydrogen chloride in the process is a big problem.

In order to solve this problem, the inventors of the present invention have proposed a technique of supplying hydrogen chloride in an exhaust gas to a conversion reaction with dichlorosilane coexisting in the same exhaust gas in the presence of an activated carbon catalyst. To remove (Japanese Patent No. 3853894). According to this technique, the hydrogen chloride in the exhaust gas can be efficiently removed, and the trichlorosilane which is regenerated by the conversion reaction of hydrogen chloride and dichlorosilane can be recycled as a raw material of the crucible, and further, activated carbon The life of the catalyst is also long. Therefore, in the industry, this technology is considered to be a very excellent technology and is widely used in industry.

However, as described above, in the exhaust gas discharged from the reactor, hydrogen is contained in addition to dichlorosilane and hydrogen chloride. Since the proportion of hydrogen in the exhaust gas is large, the hydrogen can be recycled industrially.

In the case of industrial production of polycrystalline germanium, the removal of hydrogen chloride in the above-mentioned exhaust gas and the recycling of hydrogen in the exhaust gas are used in combination. Specifically, hydrogen recovered from a gas obtained by supplying the exhaust gas to the treatment obtained by the above-described conversion reaction is supplied to the reactor as a part of the raw material gas for producing polycrystalline germanium. At this time, the phosphorus atom-containing impurity (phosphorus impurity) derived from the activated carbon of the conversion reaction catalyst is mixed into the recovered hydrogen to cause a situation in which the phosphorus concentration in the produced crucible is increased, which is a problem. If the concentration of phosphorus in the sputum is high, it will damage the electrical characteristics, so it is not good. When polycrystalline germanium is used, for example, in a solar cell, the allowable phosphorus concentration is approximately less than 200 ppb-wt.

Of course, the problem of an increase in the phosphorus concentration in the sputum can be improved by using activated carbon having a low phosphorus content as a conversion reaction catalyst. However, generally as a worker The activated carbon used in industrial catalysts is derived from coconut shells, charcoal, etc., and usually contains about 200 ppm-wt of phosphorus atoms. There is a technique of reducing the concentration of phosphorus in activated carbon by washing activated carbon with acid. This technology, in addition to cost problems in equipment and operation, can only reduce the phosphorus concentration in the activated carbon to about 50 ppm-wt by acid washing. Therefore, the problem of the phosphorus concentration in the sputum must be improved by a method other than reducing the concentration of phosphorus in the activated carbon.

In the above, "ppb-wt" means a unit of 1 part per billion by weight, and "ppm-wt" means a unit of 1 part per million by weight (the same applies to the following description).

Accordingly, an object of the present invention is to provide a method for producing polycrystalline silicon, which comprises the steps of removing hydrogen chloride in an exhaust gas, and recycling the hydrogen recovered by the exhaust gas to a step of decanting, which is easy and Phosphorus impurities from the activated carbon catalyst are efficiently removed.

The inventors of the present invention have diligently studied in order to solve the above problems. The inventors of the present invention first traced that the phosphorus impurity derived from activated carbon has a chemical tendency to easily form a form such as PCl ₃ or PH ₃ in the coexistence of a chlorodecane compound, hydrogen chloride, and hydrogen. Next, attention is paid to these compounds, and since they have an isolated electron pair on the phosphorus atom, they act as a Lewis base. Therefore, it has been found that the phosphorus gas is efficiently removed as a result of bringing the gas supplied to the conversion reaction or the hydrogen separated from the gas into contact with the Lewis acidic compound, and thus the present invention has been completed.

That is, the present invention relates to a method for producing a polycrystalline silicon, which comprises a step of forming a ruthenium by reacting a chlorodecane compound with hydrogen, and contacting the exhaust gas discharged from the hydrazine precipitation step with activated carbon. a conversion reaction step of removing hydrogen chloride in the exhaust gas, a separation step of separating hydrogen in the gas after the conversion reaction obtained by the above-mentioned conversion reaction step, and a polycrystal having a hydrogen obtained by the separation step supplied to the cycle of the decantation step a manufacturing method; characterized in that at least one of the following conditions (1) and (2) is satisfied, (1) the gas after the conversion reaction obtained by the conversion reaction step, and the Lewis-containing acidic compound are supplied before the separation step The adsorbent is contacted and (2) the hydrogen obtained in the separation step is brought into contact with the adsorbent containing the Lewis acidic compound before being supplied to the ruthenium precipitation step.

The method for producing a polycrystalline silicon used in the present invention comprises the steps of: forming a ruthenium by a reaction of a chlorodecane compound with hydrogen, and contacting the exhaust gas discharged from the hydrazine precipitation step with activated carbon; a conversion reaction step of removing hydrogen chloride in the exhaust gas, and separating the gas after the conversion reaction obtained by the foregoing conversion reaction step The hydrogen separation step and the hydrogen obtained by the separation step are supplied to the circulation step of the above-described decantation step.

<矽 precipitation step>

The hydrazine precipitation step is a step of forming hydrazine by a reaction of a chlorodecane compound with hydrogen, and specifically, for example, a Siemens method (bell cover method) or a gas-liquid deposition method (VLD method = Vapor to Liquid) Deposition method) and so on.

In the above-mentioned Siemens method, the core wire provided in the reactor (bell jar) is heated to a high temperature (for example, 600 to 1200 ° C) higher than the enthalpy precipitation temperature, and is brought into contact with a raw material gas containing a chlorosilane compound and hydrogen, thereby A batch method in which the surface of the above-mentioned core wire is precipitated.

In the gas-liquid deposition method, the substrate provided in the reactor is heated to a high temperature (for example, 600 ° C or higher) at a temperature equal to or higher than the precipitation temperature, and a raw material gas containing a chlorosilane compound and hydrogen is passed through the substrate. After the surface of the substrate is precipitated, the substrate is maintained at a high temperature (for example, 1450 to 1700 ° C) which is higher than the melting point of the crucible, and the precipitated crucible is melted and dropped to recover the successive method; or, it is set in the reaction. The substrate in the device is heated to a high temperature (for example, 1450 to 1700 ° C) above the melting point of the crucible, and a raw material gas containing a chlorodecane compound and hydrogen is passed through the substrate to precipitate the crucible on the surface of the substrate. A continuous process of melting down.

The chlorodecane compound contained in the above-mentioned source gas may, for example, be chlorosilane or methylene chloride, and particularly preferably chlorosilane. The above raw material gas The concentration of hydrogen contained in the mixture is an excess amount with respect to the decane compound, and may be, for example, 5 mol or more per mol of the chlorodecane compound.

<Conversion reaction step>

In the conversion reaction step, the exhaust gas discharged from the above-described decanting step is contacted with activated carbon to remove hydrogen chloride in the exhaust gas.

The exhaust gas contains at least a chlorodecane compound, hydrogen, and hydrogen chloride. The chlorodecane compound is composed of a thermally decomposed product of a chlorodecane compound contained in a material gas and an unreacted chlorodecane compound, and contains, for example, tetrachlorosilane, trichlorodecane, dichloromethane, monochlorodecane, One or more of hexachlorodioxane and pentachlorodioxane. Hydrogen is composed of hydrogen generated by thermal decomposition of a chlorodecane compound contained in a material gas and unreacted hydrogen. Hydrogen chloride is a product derived from the aspiration reaction of hydrazine. The concentration of hydrogen chloride in the exhaust gas is, for example, 0.1 to 6 mol%, particularly 0.2 to 3 mol%.

In the conversion reaction step of the present invention, hydrogen chloride in the exhaust gas is removed by a conversion reaction with a chlorodecane compound contained in the same exhaust gas. Hereinafter, an example of a conversion reaction will be mentioned.

The main reaction when the chlorodecane compound is methylene chloride: HCl + SiH ₂ Cl ₂ → SiHCl ₃ + H ₂

The main reaction when the chlorodecane compound is hexachlorodioxane: HCl + SiCl ₆ → SiHCl ₃ + SiCl ₄

The main reaction when the chlorodecane compound is pentachlorodioxane: HCl + SiHCl ₅ → 2SiHCl ₃

The conversion reaction can also be carried out by adding a chlorodecane compound to the exhaust gas. The additional chlorodecane compound is used for the purpose of improving the removal efficiency of hydrogen chloride contained in the exhaust gas. Therefore, it is not particularly limited as long as it can be reacted with hydrogen chloride. As the additional chloromethane compound, for example, trichlorodecane, dichloromethane, monochlorodecane or the like can be used. The total amount of the chloromethane compound is a total amount of the chloromethane compound after the addition, and is preferably 1 mol or more, preferably 1.2 mol or more, based on 1 mol of hydrogen chloride contained in the exhaust gas. The total amount of the added chlorodecane compound is preferably 1.5 m or less from 1 mol of hydrogen chloride contained in the exhaust gas from the viewpoint of maintaining the volume of the circulating gas in an appropriate range.

The above conversion reaction is catalyzed by activated carbon. The activated carbon of the conversion reaction catalyst is preferably activated carbon having a pore distribution property. Specifically, from the viewpoint of efficiently performing the conversion reaction, it is preferred to use a pore radius (R) having a maximum peak in the pore distribution curve obtained by the steam adsorption method to be 1.2 × 10 ^-9 to 4.0 × 10 ^-9 activated carbon. The specific surface area of the activated carbon is preferably 500 m ² /g or more from the viewpoint of improving the contact efficiency of the gas to efficiently carry out the addition reaction. The specific surface area of the activated carbon is more preferably 600 to 1000 m ² /g. The above specific surface area is a value measured by a BET method using nitrogen as an adsorbate (the same applies hereinafter).

The shape of the activated carbon is not particularly limited, and for example, it is preferably a shape having a granular shape, a honeycomb shape, or a fibrous shape. The size of the activated carbon is preferably from 1 to 5 mm in terms of ease of handling.

The activated carbon used in the conversion reaction step in the present invention is contained Phosphorus is a prerequisite. Therefore, the activated carbon as a conversion reaction catalyst may be derived from coconut shell, charcoal or the like. The activated carbon used in the industry today contains about 200 ppm-wt of phosphorus atoms, and the phosphorus content of the resulting polycrystalline germanium is generally increased to such an extent that the electrical properties of the crucible are not impaired. Therefore, in the present invention, in order to remove hydrogen chloride, an industrial antimony precipitation method using activated carbon is generally applicable.

Activated carbon is generally easy to adsorb moisture in the air. When the activated carbon adsorbed with water is supplied to the conversion reaction step, the water reacts with the chlorodecane compound in the exhaust gas to form a ruthenium compound on the activated carbon. When a phthalic acid compound is formed on the activated carbon, problems such as clogging and contamination of the piping may occur, which is not preferable. Therefore, the activated carbon is preferably supplied to the conversion reaction after removing the adsorbed water. The method of removing moisture may, for example, be at least one of pressure reduction and heating. This pressure reduction treatment can be carried out by maintaining the pressure under an absolute pressure of, for example, 1 × 10 ⁴ Pa or less, preferably 1 × 10 ³ Pa or less. The heat treatment can be carried out, for example, at 80 to 130 ° C for a certain period of time. This heat treatment is preferably carried out under a flow of an inert gas or under reduced pressure. Examples of the inert gas to be used include nitrogen, helium, argon, and the like. The degree of pressure reduction when it is carried out under reduced pressure is the same as the degree of pressure reduction in the above-described pressure reduction treatment.

The pressure reduction treatment and the heat treatment are preferably carried out until the water in the activated carbon is sufficiently removed. Whether the moisture is sufficiently removed can be confirmed by measuring the dew point of the ambient atmosphere. The removal of moisture is preferably carried out until the dew point of the ambient atmosphere is -30 ° C or lower, more preferably -40 ° C or lower.

Reaction temperature, reaction time, reaction pressure, etc. of the conversion reaction, visible The concentration of hydrogen chloride and chlorodecane compound in the exhaust gas is appropriately set. Specifically, it is as follows.

Reaction temperature: preferably 60 to 250 ° C, more preferably 100 to 200 ° C

Reaction time (residence time): preferably 0.5 to 30 seconds, more preferably 5 to 15 seconds

The contact time (reaction time) of the activated carbon and hydrogen chloride in the removal of hydrogen chloride is preferably such that the diameter of the contact bed, the amount of activated carbon used, and the flow rate of the gas are relatively adjusted so as to have the above range.

Hydrogen chloride in the exhaust gas can be efficiently removed by the above-described conversion reaction. The concentration of hydrogen chloride in the exhaust gas after the conversion reaction is preferably 0.1 mol% or less.

This transformation reaction is an exothermic reaction. Therefore, the vent gas system supplied to the conversion reaction is contacted with the activated carbon at a high temperature. Therefore, the phosphorus impurities in the activated carbon are mixed into the gas after the conversion reaction. In the method of the present invention, the phosphorus impurities contained in the gas after the conversion reaction may be, for example, PCl ₃ or PH ₃ , and may contain one or more of these. The concentration of the phosphorus impurities in the gas after the conversion reaction is converted into a phosphorus atom and is approximately 200 to 2000 ppb-wt.

<Separation step>

In the separation step, the gas after the conversion reaction obtained by the above conversion reaction step separates hydrogen. The gas after the conversion reaction contains at least hydrogen and a chlorodecane compound. The chlorodecane compound contains a thermal decomposition product of a chlorosilane compound contained in a raw material gas, an unreacted chlorodecane compound, and a chloromethane compound (and a phosphorus impurity) formed in the conversion reaction. Specifically In other words, it includes, for example, tetrachlorosilane, trichlorodecane, dichlorodecane, monochlorodecane, hexachlorodioxane, pentachlorodioxane, and the like.

Therefore, the separation step, in essence, is a step of separating hydrogen from the chlorodecane compound by the gas after the conversion reaction.

When the hydrogen is separated from the chlorosilane compound by the gas after the conversion reaction, a well-known means can be used without limitation. For example, a method in which the gas after the conversion reaction is cooled to liquefy the chlorodecane compound, thereby separating the hydrogen from the hydrogen. The cooling is carried out so that the gas after the conversion reaction reaches a temperature of preferably -10 ° C or lower, more preferably -40 ° C to -20 ° C.

<loop step>

In the recycling step, the hydrogen obtained in the above separation step is recycled and supplied to the above-described decanting step. When the separated hydrogen is supplied to the hydrazine precipitation step, for example, a means of circulating by a compressor or the like can be mentioned. The compressor may, for example, be a turbo compressor or a volume compressor.

At this time, the chlorodecane compound obtained by the above separation step may be purified as necessary, and then supplied to the above-described hydrazine precipitation step. The method for purifying the chlorodecane compound obtained in the separation step may, for example, be distillation. When the chlorodecane compound is recycled to the hydrazine precipitation step, the chlorodecane compound is preferably supplied to the hydrazine precipitation step via a line different from the hydrogen circulation line.

<Adsorbent material containing Lewis acidic compound>

The method of the present invention is a method for producing a polycrystalline silicon containing the steps described above, characterized in that at least one of the following conditions (1) and (2) is satisfied By.

(1) before the separation step, contacting the gas after the conversion reaction obtained by the conversion reaction step with the adsorption material containing the Lewis acidic compound, and (2) supplying the hydrogen obtained in the separation step before the supply to the ruthenium precipitation step, The adsorbent material containing the Lewis acidic compound is contacted.

By satisfying the above conditions, the phosphorus impurities derived from the activated carbon contained in the gas after the conversion reaction can be efficiently removed, whereby the content of germanium atoms in the obtained polycrystalline germanium can be reduced as much as possible.

The adsorbent used in the present invention contains a Lewis acidic compound.

The Lewis acidic compound may, for example, be AlCl ₃ , Al ₂ (SO ₄ ) ₃ , CuSO ₄ or NiSO ₄ , and one or more selected from the above may be used. Among these, it is preferable to use CuSO ₄ from the viewpoint that the effect of removing phosphorus impurities is extremely high.

The Lewis acidic compound as described above may be used as it is in this state, or may be used in a state of being impregnated with a substrate. By using a Lewis acidic compound in a state of being attached to a substrate, the effective surface area of the Lewis acidic compound can be increased, whereby the removal efficiency of the phosphorus impurity is extremely high, which is preferable.

Examples of the substrate include silicone, zeolite, and alumina. As the above zeolite, any of natural zeolite and synthetic zeolite (for example, molecular sieve or the like) can be used.

The specific surface area of the substrate is preferably 50 m ² /g or more, more preferably 80 to 1000 m ² /g or more, and particularly preferably 100 to 500 m ² /g.

The substrate, preferably, is classified into a particle size range of about 1 to 5 mm. Pay by credit.

A method of adding a Lewis acidic compound to a substrate can be carried out by a known means. For example, a method in which a Lewis acidic compound is dissolved in a suitable solvent to prepare a solution, a substrate is impregnated into the solution, or the solution is allowed to stand on a substrate, and then heated to remove the solvent. The solvent of the above solution may, for example, be water.

When the addition of the Lewis acidic compound to the substrate is carried out by an impregnation method, the concentration of the Lewis acidic compound in the above solution can be appropriately adjusted depending on the desired amount of addition. For example, when the amount of addition is 5 wt%, the concentration of the Lewis acidic compound in the above solution is preferably 10 to 20% by weight. The amount of the solution used in the impregnation is preferably such that the substrate can be completely flooded with the solution in the impregnation vessel. The impregnation temperature is as long as it is carried out at room temperature, and does not require special heating or cooling. The impregnation time is preferably 6 to 36 hours. After the impregnated substrate is separated from the solution by a suitable method, for example, filtration, it is preferably washed with a solvent and then heated to remove the solvent. The solvent used herein is preferably the same type as the solvent of the Lewis acidic compound solution. The heating temperature is preferably 130 or more. Heating is preferably carried out under the circulation of an inert gas. The inert gas used herein may, for example, be nitrogen, helium or argon. This heating is preferably carried out until the solvent is sufficiently removed. The removal of the solvent is preferably carried out until the dew point of the substrate after heating in an inert gas is -30 ° C or lower, and the value is more preferably -40 ° C or lower.

The amount of the Lewis acidic compound to be added to the substrate can be appropriately set depending on the concentration of the phosphorus impurity to be removed, and the weight can be made with respect to the weight of the substrate. It is 1 to 20% by weight, preferably 3 to 15% by weight. The amount of the addition can be measured by, for example, elemental analysis, fluorescent X-ray analysis, or the like. The amount of addition can be controlled, for example, by changing the concentration of the Lewis acidic compound solution used, the substrate temperature at the time of impregnation or the dispersion, and the like. Appropriate addition conditions are readily known by those skilled in the art with some preliminary experiments.

The adsorbent material prepared by adding a Lewis acidic compound to the substrate is preferably used in a particle size range of about 1 to 5 mm.

The substrate in the adsorbent material as described above easily absorbs moisture in the air. Therefore, when the adsorbent material is supplied to the gas after the conversion reaction before the separation step, it is preferred to remove the adsorbed moisture in advance. This treatment is to prevent the chlorodecane compound contained in the gas after the conversion reaction before the separation step from reacting with the adsorbed water to form a cerium oxide, thereby causing a decrease in the adsorption activity due to the coating of the surface of the adsorbent, blocking of the pipe, and contamination. Those who are in a bad situation.

On the other hand, when an adsorbent prepared by adding a Lewis acidic compound to the substrate is supplied and supplied with hydrogen after the separation step, no ruthenium oxide is formed at the time of contact. However, the detached adsorbed water has a reactor that is transported together with the treated hydrogen. Since the chloromethane compound is present in the reactor, there is still a enthalpy of formation of cerium oxide. Therefore, in this case, it is preferable to carry out the moisture removal treatment in advance.

The method of removing moisture may, for example, be at least one of pressure reduction and heating. The method and extent of the reduced pressure treatment are the same as the method and extent of removal of the moisture of the activated carbon described above.

The substrate which can be preferably used in the present invention contains a ruthenium atom and an aluminum atom. At least one of them. When the surface of the adsorbent material prepared by such a substrate is used, there is a case where M-OH (M is a ruthenium or aluminum) group remains.

If the adsorbent having a surface M-OH group is supplied to the gas after the conversion reaction before the separation step, the M-OH group will react violently with the chlorosilane compound to emit heat exceeding the heat resistance of the reaction vessel. , which will damage the reaction vessel. When M is a deuterium atom, the tendency to heat is more pronounced. In order to avoid such a situation, it is preferred to perform the deactivation treatment of the M-OH group on the surface of the adsorbent before supplying the adsorbent to the gas after the conversion reaction before the separation step.

When the M-OH group on the surface of the adsorbent is deactivated, it can be brought into contact with an appropriate M-OH bond deactivator by the adsorbent. The contacting can be carried out in the liquid phase or in the gas phase. However, it is preferable to carry out in the vapor phase for reasons such as simple operation and no post-treatment.

The deactivating agent used for the deactivation of the surface M-OH group can be used without any particular limitation as long as the bond can be inactivated. However, when it is considered that there is a possibility that the deactivating agent remains in the mixing step if it remains on the adsorbent, it is preferred to use the species present in the step as a deactivating agent. Such a deactivating agent is preferably a chlorodecane compound. Specific examples of the above chlorodecane compound include dichlorosilane, trichlorodecane, tetrachlorosilane, and the like. Among these, the deactivation of the M-OH bond can be stably carried out by using tetrachlorosilane having the lowest reactivity with the M-OH bond, which is preferable.

When the surface M-OH group is deactivated in the vapor phase, it can be brought into contact with a mixed gas of the above-mentioned chlorodecane compound and an inert gas. The concentration of the chlorodecane compound in the mixed gas is preferably 0.5 vol% or less, more preferably 0.1 to 0.3 vol%. The inert gas to be mixed with the chlorosilane compound may, for example, be nitrogen, helium or argon.

The conditions for bringing the adsorbent and the deactivator into contact with the gas phase can be appropriately set depending on the concentration of the surface M-OH group, the amount of the adsorbent used, the type and concentration of the deactivator used, and the like. Make a general decision. However, the general conditions can be as disclosed below.

The temperature at which the deactivating agent is in contact: preferably 20 to 100 ° C, more preferably 40 to 80 ° C.

Inactivation agent contact time (residence time): preferably 30 to 120 seconds

When a chlorodecane compound is used as the deactivating agent, the reaction of the chlorodecane compound with the surface M-OH group is an exothermic reaction. Therefore, the end of the deactivation reaction can be understood by monitoring the temperature change in the vicinity of the adsorbent.

<Contact with adsorbent material>

The present invention relates to a method for producing a polycrystalline germanium comprising a deuterium precipitation step, a conversion reaction step, a separation step and a recycle step, characterized in that at least one of the following conditions (1) and (2) is satisfied: (1) separation Before the step, the gas obtained by the conversion reaction step is brought into contact with the adsorbent material containing the Lewis acidic compound, and (2) the hydrogen obtained in the separation step and the Lewis acid-containing compound are supplied before the step of supplying to the ruthenium precipitation step. Adsorbed material is in contact.

As described above, the gas after the conversion reaction is mixed with phosphorus impurities derived from activated carbon. The inventors of the present invention confirmed that the phosphorus impurity is also contained in the hydrogen after the separation step. On the other hand, in the chlorodecane compound after the separation step, it does not contain There is such a phosphorus impurity, or even if it is contained, it is a trace amount.

Therefore, when the phosphorus impurities are removed by the regeneration gas recycled by the decantation step, at least one of the above conditions (1) and (2) may be satisfied.

The contact conditions in the above conditions (1) and (2) are not particularly limited.

The form of the contact may be, for example, a method in which an adsorption reaction vessel having an adsorbent material in a suitable form such as a fixed bed or a fluidized bed is used, and the gas after the conversion reaction is separately flowed under the conditions (1) and (2). And the hydrogen obtained by the separation step, thereby contacting the adsorbent material with the gas.

The temperature at the time of contact is not particularly limited. However, it is preferable that the heat-resistant temperature of the material constituting the contact reaction layer is not more than the heat-resistant temperature of the substrate, and when the Lewis acid compound is applied to the adsorbent material formed on the substrate, it is preferably at least the heat-resistant temperature of the substrate. On the other hand, in the case of the condition (1), since the gas after the conversion reaction obtained by the conversion reaction step of the exothermic reaction is used, if the contact temperature is set too low, the degree of cooling necessary is too large. The loss of thermal energy becomes meaningless. From the above point of view, the contact temperature is preferably -40 to 200 ° C, more preferably 50 to 200 ° C, and particularly preferably 80 to 150 ° C.

The contact time (residence time) is preferably 1 second or longer. Since the effect of the longer contact time is not reduced, the upper limit of the contact time is not limited. However, considering industrial convenience, it is preferably 30 seconds or less. A better contact time is 5 to 15 seconds.

The pressure at the time of contact is not particularly limited. The contact pressure can be, for example, 200 to 2000 kPa.

In the present invention, it is preferable that only the above condition (1) is satisfied and the condition (2) is not satisfied. The reason for this is that if the gas is brought into contact with the adsorbent after the conversion reaction, the chlorodecane compound contained in the gas after the conversion reaction is adsorbed to the adsorbent, and the life of the adsorbent is impaired.

The conditions for industrially advantageous carrying out the process of the present invention are as described above. However, the effects of the present invention have been confirmed to be less susceptible to changes in temperature and pressure at the time of contact of the adsorbent with the gas. This tendency is one of the very advantageous features shown by the present invention. That is, since the temperature and pressure at the time of contact are not easily affected, the reaction conditions of the contact reaction need not be specifically controlled, and the contact position of the adsorbent with the gas can be set to an arbitrary position. The contact position, for example, in the case of the above condition (1), can be set to any position between the conversion reaction step and the separation step; in the case of the above condition (2), it can be set after the separation step. Hydrogen is supplied to any of the cyclic steps of the decantation step.

Example <Preparation Example of Adsorbent> Modulation example 1

In a container having a capacity of 500 mL, 100 g of a granular tantalum having a specific surface area of 250 m ² /g and an average particle diameter of 3 mm was charged. 100 mL of a 20 wt% CuSO ₄ aqueous solution obtained by dissolving copper sulfate 5 hydrate in ion-exchanged water was added thereto, and immersed at 25 ° C for 24 hours. The impregnated silica gel was collected by filtration, washed with ion-exchanged water, and heated at 130 ° C for 24 hours under a nitrogen atmosphere to obtain an adsorbent (10 wt% CuSO ₄ -added silicone).

Modulation example 2

In the above-mentioned preparation example 1, an absorbent material was obtained in the same manner as in Preparation Example 1 except that 100 mL of a 20% by weight aqueous solution of NiSO ₄ obtained by dissolving nickel sulfate hexahydrate in an ion-exchanged water in an aqueous solution of CuSO ₄ was used. (10wt% NiSO _{4 is added with} silicone).

Modulation example 3

In the above-mentioned preparation example 1, the same procedure as in Preparation Example 1 was carried out, except that 100 mL of an Al ₂ (SO ₄ ) ₃ aqueous solution having a concentration of 20% by weight of the aluminum sulfate 16 hydrate obtained by dissolving the aluminum sulfate 16 hydrate in the aqueous solution of the CuSO _{4 was} used. An adsorbent (10 wt% Al ₂ (SO ₄ ) _{3 was added to the} silicone) was prepared.

Modulation example 4

In the above-mentioned preparation example 1, an absorbent material (10 wt%) was obtained in the same manner as in Preparation Example 1 except that 100 g of granular activated alumina having a specific surface area of 180 m ² /g and an average particle diameter of 3 mm was used instead of the granular tannin. CuSO _{4 is added with} alumina).

Modulation example 5

In the above-mentioned preparation example 1, an adsorbent (10 wt% CuSO ₄ ) was obtained in the same manner as in Preparation Example 1 except that 100 g of a granular zeolite having a specific surface area of 180 m ² /g and an average particle diameter of 3 mm was used instead of the granular tannin. Add zeolite).

Modulation example 6

In the above-mentioned preparation example 1, an adsorbent (3 wt% CuSO _4-added tannin) was obtained in the same manner as in Preparation Example 1 except that the concentration of the CuSO ₄ aqueous solution was 5% by weight.

Modulation example 7

In the above-mentioned preparation example 1, an adsorption material (15 wt% CuSO _4-added silicone) was obtained in the same manner as in Preparation Example 1 except that the concentration of the CuSO ₄ aqueous solution was 30% by weight.

<General Experimental Methods>

In the following examples, hydrogen containing a predetermined amount of hydrogen chloride and methylene chloride was used as a mode gas for the exhaust gas discharged from the ruthenium precipitation step.

The above-mentioned mode gas is circulated on the conversion reaction catalyst to carry out a conversion reaction. The hydrogen separated by the gas after the conversion reaction obtained by the conversion reaction step is brought into contact with the adsorbent by circulating on a predetermined adsorbent. Next, a gas obtained by mixing trichloromethane with hydrogen after contact with the adsorbent was used as a raw material, and a decantation step was carried out by a Siemens method, and the concentration of phosphorus in the obtained polycrystalline germanium was measured.

The detailed experimental method is as follows.

(1) Conversion reaction step

Using a granular activated carbon having a specific pore diameter (R) of 1.2 × 10 ^-9 m and an average particle diameter of 3 mm, which has a specific surface area of 1,300 m ² /g and a pore distribution curve obtained by a water vapor adsorption method, Conversion reaction catalyst. The activated carbon is derived from a coconut shell having a phosphorus atom content of 200 ppm-wt.

A cylindrical stainless steel container having an inner diameter of 27 mm and a length of 100 mm was filled with 10 g of the above activated carbon, and a thermocouple was inserted into the container. The thermocouple is used to determine the temperature of the activated carbon filling layer.

First, the removal of moisture adsorbed to the activated carbon is performed. The activated carbon layer was heated to 150 ° C, and the dried nitrogen was flowed at a pressure of 2 kPa G at a flow rate of 0.05 NL / min for 10 hours to remove adsorbed moisture. Next, the inside of the vessel was replaced with hydrogen, and while the temperature of the activated carbon layer was cooled to 30 ° C, it was supplied to the conversion reaction.

The conversion reaction was carried out using hydrogen gas containing 1.5 mol% each of hydrogen chloride and dichlorosilane as a mode gas. This mode gas was passed through an activated carbon layer at a temperature of 30 ° C at a flow rate of 320 NmL/min at a pressure of 1 kPaG. At this time, the temperature of the activated carbon layer rises to about 60 °C. The consideration is due to the heat of adsorption of activated carbon and the heat of reaction of the conversion reaction.

(2) Separation step

The gas discharged from the above conversion reaction is cooled at a temperature of -40 ° C, and then the gas phase is recovered to separate hydrogen. The phosphorus atom concentration in the obtained hydrogen was 2000 ppb-wt.

(3) Step of contacting hydrogen with adsorbent

A cylindrical stainless steel container having an inner diameter of 27 mm and a length of 100 mm was filled with a predetermined adsorbent material of 10 g, and a thermocouple was inserted into the container.

First, after removing the moisture adsorbed on the adsorbent, the surface M-OH is performed. Inactivation of the key.

The adsorbent layer was heated to 150 ° C, and the dried nitrogen was flowed at a flow rate of 0.05 L/min for 10 hours to remove adsorbed moisture. Next, nitrogen containing 0.5 vol% of tetrachloromethane was flowed at a flow rate of 10 kPaG at a flow rate of 10 kPaG for 5 hours. Thereafter, it is supplied to contact with hydrogen.

After the temperature of the adsorbent layer after the treatment is set to a predetermined temperature, the hydrogen obtained in the separation step is passed at a predetermined flow rate at a pressure of 1 kPa G to carry out a contact reaction between hydrogen and the adsorbent.

(4) Steps of precipitation

The hydrogen obtained in the above contacting step was mixed with trichloromethane to prepare a mixed gas of hydrogen: trichlorodecane = 10:1 (volume ratio). This mixed gas was supplied to a crucible tube having a diameter of 8 mm and a length of 100 mm heated to 1200 ° C, whereby the polycrystal was decanted out of the surface of the manifold.

The concentration of phosphorus atoms in the obtained polycrystalline germanium was determined by elemental analysis.

Reference Example 1 (blank test)

The polycrystalline silicon was produced in the same manner as in the above "(4) hydrazine precipitation step, except that hydrogen containing no phosphorus impurities was used as the raw material hydrogen.

The phosphorus atom concentration in the obtained polycrystalline germanium is shown in Table 1.

Comparative Example 1 (when no adsorbent material is used)

In the above "(3) Contact step of hydrogen and adsorbent material", the container is made into an empty container without using an adsorbent, and the temperature of the empty container is set to 80 ° C to carry out the contacting step, and Experimental method > same The sample is operated to make a crystal.

The phosphorus atom concentration in the obtained polycrystalline germanium is shown in Table 1.

Examples 1 to 10 and Comparative Examples 2 and 3

The type of the adsorbent in the step (3) the step of contacting the hydrogen with the adsorbent, the temperature of the adsorbent layer, and the hydrogen flow rate are as described in Table 1, and the respective steps are carried out in accordance with the above-mentioned <general experimental method>. It is much more crystalline.

The phosphorus atom concentration in the obtained polycrystalline germanium is shown in Table 1, respectively.

The silicone and activated alumina used in Comparative Examples 2 and 3 are as follows.

Silicone (Comparative Example 2): Granular silicone having a specific surface area of 250 m ² /g and an average particle diameter of 3 mm.

Activated alumina (Comparative Example 3): Granular activated alumina having a specific surface area of 180 m ² /g and an average particle diameter of 3 mm.

According to the present invention, in the method for producing polycrystalline silicon by the reaction of a chlorodecane compound and hydrogen, the combined use of the removal of hydrogen chloride in the exhaust gas and the recycling of hydrogen in the exhaust gas can easily and efficiently remove the circulating gas. Contains phosphorus impurities from activated carbon catalysts. Therefore, the polycrystalline silicon obtained by the above method of the present invention can be used for solar cells, semiconductors, etc., by reducing the phosphorus atom content as much as possible.

Claims (5)

A method for producing polycrystalline germanium, comprising: a step of forming a ruthenium by reacting a chlorodecane compound with hydrogen; and contacting the exhaust gas discharged from the mashing step with activated carbon to remove hydrogen chloride in the exhaust gas a conversion reaction step, a separation step of separating hydrogen in the gas after the conversion reaction obtained by the above-mentioned conversion reaction step, and a method for producing polycrystalline silicon obtained by supplying the hydrogen obtained in the separation step to the cycle of the above-described decantation step; Satisfying at least one of the following conditions (1) and (2), (1) contacting the gas after the conversion reaction obtained by the conversion reaction step with the adsorption material containing the Lewis acidic compound before the separation step, and (2) Before the supply to the deuterium precipitation step, the hydrogen obtained in the separation step is brought into contact with the adsorption material containing the Lewis acidic compound. The method for producing a polycrystalline silicon according to the first aspect of the invention, wherein the Lewis acid compound is at least one selected from the group consisting of CuSO ₄ , NiSO ₄ and Al ₂ (SO ₄ ) ₃ . The method for producing a polycrystalline silicon according to claim 1 or 2, wherein the adsorbing material is an adsorbent obtained by adding a Lewis acid compound to a substrate. The method for producing a polycrystalline silicon according to the third aspect of the invention, wherein the substrate is at least one selected from the group consisting of cerium oxide gel, molecular sieve, zeolite, and alumina. The method for producing a polycrystalline silicon according to the fourth aspect of the invention, wherein the adsorbing material is supplied to a treatment with a chlorodecane compound.